Surely some to Charity, pay of any debts, early retirement, future kids fund, and i am sure that some portion will go to Astronomy. Ah who am i kidding all of it to Astronomy.
Build a TARDIS, or at least a means of Intergalactic Travel. Travel between the stars, seek out.. I think deep within us all there is some thing that turns us to the heavens and seek out.. a lottry ticket might not be enought though, but with a TARDIS you could make a few Stock Speculations
Or Pehaps get Leonardo to paint a Few more Mona Lisa's and hide them.... Sorry i am presently going through the Tom Baker season so forgive me.
Oh but wait i have not bought a lotto ticket in ages.
Regards